Automatic control of electrical furnaces



T. E. NIBLOCK.

AUTOMATIC CONTROL OF ELECTRICAL FURNACES.

APPLICAHON nun rm. 8. 1921.

1, 130, 104, Patgfite Se t. 26, 1922.

Patented Sept. 26, 1922.

UNITED ,sTArss PATENT OFFICE.

THOMAS E. NIBLOCK, OF GREAT FALLS, MONTANA.

AUTOMATIC CONTROL or ELECTRICAL someone.

Application filed February a, .1921. Serial No. 443,419.

To all whom it may concern:

Be it known that I, THOMAS E. NrBLooK, a citizen of the United States, residing at Great Falls, in the county of Cascade and State of Montana, have invented certain new and useful Improvements in Automatic Controls of Electrical Furnaces, of which the following is a specification.

This invention relates to an automatic control of electrical furnaces and more particularly to that type of furnaces in which the electrodes are raised and lowered by means of an electrically driven winch. r I

This invention is primarily intended for controlling and regulating the lowering of electrodes into a charge of high electrical resistance.

The objects and the operation of the 'in vention will appear more clearly from the specification and the drawings forming part Of it. i 1

In the drawing Fig. 1 is a more or less diagrammatic view 0 an arrangement embodying the invention; and Fig. 2 is a fragmentary plan view of a detail.

In the drawings 1 is a furnace and 2 the electrodes supported by chains 3 above the furnace. Upon a suitable supporting frame 4 is mounted the winch 5 and the electric motor 6 driving the latter. The chains 3 pass over pulleys 7 and around sheaves 8 and have their ends connected to the frame-4E. It is understood, however, that the particular form of support of the electrodes upon the chains is not material to the invention.

In the arrangement illustrated the electrodes are to be so positioned. in relation to the charge in the furnace that a certain po tential dilference exists between them and the carbon bed of the furnace or ground or neutral. Consequently the electrodes are'to be successively lowered to maintain this potential difference during the operation of the furnace. a

In order to control the movement of the electrodes I provide between the electrodes 2 and the bed of the furnace a circuit including current-responsive means for indicating the potential ditlerence. As indicated, the circuit starts from the electrode holder 9, includes a rheostat lO, a solenoid l1 and terminates at the terminal 12 connected to the carbon bed.

The solenoid 11 acts upon a plunger 13 suspended from a beam'll, the beam being supported upon a-fulcrum 15."Tl'1 beam carries-contact pieces 16 and 17 adapted to contact-with stationary contacts 18 and 19 respectively. Contact pieces 18 and 19 are separately connected to one side of a low voltage d rect-ecurrent" bu'sb'ar 27 .through solenoids 20 and 21;-- Solenoid 20 actuates a plu er 22'w-h1ch"is operatively connected to a ouble pole switch 25, while solenoid 21 actuates a plunger 23 connected toi'a similar switch 26. A connection 24'leads fromthe otherl s de of the busbar to the fulcrum of the beard-14a The switchesj25and 26 and the armature of the-motor ti are sointerconnected '1 that when one switch is closed current passes through'the'armature of the motor in one direction 'and whenthe other switch is closed, current passes through motor in opposite direct-ion;

The mechanism -so-'far described operates as follows: j T l So-long as the potential between the holder 9 and the'terlninahl2 is normah'the current passing through-the solenoid "11 and acting on the plunger'tlii is just sulficient to hold the beam-14in balancedposition between the contacts 18 and-19. Should the potential between holder 9 and terminal 12nse,however, an increased-current will flow throu h the solenoid 1 1, causing a lifting ofthe unger and a'swmgin of a beam 14 where y contact is'establis ed between contact piece 16 and contact 18: Thereby the circuit through solenoid 20 is closed and the plunger 22 is actuated'closing switch 25. Thereupon the current from' busbar 27 flows through the armature of the motor in such a direction that the motor turns in a direction to lower the electrodes into the char e. Ordinarily this lowering movement woul continue until the POlJBDtlfll reaches the normal value whereupon the action of the solenoid 11 would again be balanced by the weight of the plunger 13 to bring the beam 14 into neutral and 19.

lines it often happens, there should be some-'dnternal furnace disturbance and a charge of high resistance is shifted into the pathof the current flowing from the electrode, the potential difference between the electrode and round or neutral becomes high, causing a owering of the electrode, as above pointed out, until the potential is again normal.

Should'the charge beneath the electrode becomeof high resistance and of suflicient position between the contacts 18' hardness, to prevent the further lowering of the electrodes, the motor'wil'l continue to operate thus completely unwindin the cable or chain by which the electro es are suspended, often 'liui'i'iih'g" tli'e' cables "01 chains and allowing the electrodes to tip over and causing a' slloit (ii i'c'iiithi' sometimes breaking the carbon electrode.

lo prevent such a possibility and to automatically operate upon the obstructing mass or body to disintegrate it I have provided the following means constituting the inveiition.

"A lever 28 is 'pivotally supported upon a standard 29 so as to have a relativelylong airin' extend: to one side of the fulcrum a rel tin-iii) short arm extending to the other side. he short arm has a counter weight 37 to slightly overbalancethe-long a m The arrangement is such that the plane of'mo'vernent of. the lever or of'a part thereof intersects the plane of travel of.-the cable or chain. As indicated in -2-*the rh' aii-m carries at its end a cross-arm'30 isposed in the pathofthe chain when it sa s.

l in the circuit between the electrode holder 9 and the terminal 12 I have inserted a switch 31 which may be opened directly or indirectl as result of the -movemeht of the'leve'r 28 when the latter isa'cted upon by the ing cable or chain. Theparticul'a'r form "0% the switch, the form of thelever and the relationshi of the parts involved-is not material provi ed'they operate to open the circuit including the 'solenoid.1-1; when the/chain sags. For'the purpose ofillustratio'n Iih ave shown in the circuit a horizontal gap defined by the terminals 32-and-33 and a bridging piece 34 carried at the end of-a resilient arm 35 which may be conveniently supported vupon the standard 29, the a'rm'35 being normally under sufiicient tension to forceth'e bridging piece 34 upon the terminals 3'2 and 33 to close the gap. 'At the-end o'f theshort arm is mounted a pin orhalnmer :16 ositioned to strike against the bridging PlGLJB 34 and lift it out of contact with the said terminals when the sagging chain depresses the long arm and thereby causes a rise of the short arm.

The operative significance of the arrangement 'ust described is as follpws:

If the electrodes should meet in their downward movement a mass or body of suificieht hardness I prevent the farther lowering of the electrodes and'at the same time of-high resistance to cause a high, potential dro between electrode and ground or neutra ,-the motor will operate ina direction to lower the electrodes but since the movement of the electrodes is arrested,the chains will-slacken and sag. The weight of thefchains thus will hear u on the long arm of the leverancl depress wh le the short arm rises causing the switch 31 to o v n. The solenoid 1 1 will be def enrgize'd. ill owing the plunger 13 to drop whereby the beam 14 is actuated to closethe cir uit thr solenoid 21 causing thelesnig ofsv'v'i't h fi and the reversing of the "llheelrains will thus be pulled taut again and the counterweight 37 will cause the turn' oithe lever 28 and the closing of the switch 31, re-energizing solenoid 11 and raising plunger 13. Th'u's so long as the obstruction -'of high resistance in terceplis'the further downward movement of tlre electrodes," thejcha'ins will-be alternately pulled taut; slightly raising the electrode away from the charge, causing an arc,'the intense heat'of.which will tend 'to burn and soften the obstructiti mass, and 'slackened causingahammer action of the electrode upon thvobstructinghod" tending to'disintegrate' 'i-tor to su'ifictent y itatthe'charge to move the-obstrdct'ing b0 y'out of the path of the electrodes. 1 a

In this manner, the, overrunnin'g of the chain is prven6edand in addition the ele trodes m operated "to automatically adj "net the conditions in the furnace to normal conditions aljter a disturbance is caused in the manner 'hieii'tioned.

In the foregoing I- have referred to the potential difl'erence between the electrodes and groundr'orneutrahas the=governin 'factor in='-the Q ration. It is understood that the particu {ti-arran ement including the automatic controlj'switch 31 may 'find equal a plicationin conhe'ction with means responsite to the rate offcu'r'reht flow through the electrodes. In other'words the current actuating eiectro-magnetic means such as'soleu'oid 1*1and plunger 13 may be derived as is well understood, from a current transfonner'conhectedm the circuit feeding the electrodes, although the'arrangement would haverto beslightly modified in some minor detail to 'bring'uboutthe proper operation ofzthe rhbt'or.

While I consider the arrangement disclosed as'wpreferredembodiment of the invention, I am fully aware that it may he carr'ied' out in various other ways.

Thus theuse-of'a winch and chain is particularly adapted for slightly raising the electrode-away from" the charge, causing an arc. the intense heat of which will ten'd to burn-and soften theobstructin-g mass and imparting a hammer action to the'electrode's, butt-he i'd'e'a'of imparting such action may be executerlwin connection with other provisions for raising-and lowering'th'e' electrodes.

'In th'eipreferi'ed embodiment I use a chain so dispose'd th'aba portion thereof has a mere or lss horizontial position-w cause asa gin' when the tension is released. Within the scope ofpthe invention, however; the change of-t3ension maybe'translated under difi'rtit conditionsand kby difierent meansto cailse the operation of the switch 31 or its equivalent.

In the claims the term chain is intended to cover any flexible suspension means in the I nature of a chain or cable.

I claim:

1. In a system for automatically controlling the movement of electrodes in an electric furnace, the combination with means responsive to electrical conditions in the furnace to adjust the position of an electrode in the furnace, of means operative when the downward movement of the electrode is obstructed to slightly raise the electrode causing an arc and to return the electrode with a hammer action.

2. In a system for automatically controlling the movement of electrodes in an electric furnace, the combination with means responsive to electrical conditions in the furnace to adjust the position of an electrode in the furnace, of means operative when the downward movement of the electrode is obstructed to alternately raise and lower the electrode to cause successive impacts of the electrode upon the charge in the furnace.

3. In a system for automatically controlling the movement of electrodes in an electric furnace, the combination with an electrode, means for movably suspending the electrode, means for raisi and lowering the electrode, means iesponsive to electrical conditions in the furnace for controlling the movement of the electrode and means responsive to the tension in the line of suspension of the electrode for causing an alternate raising and lowering of the electrode when the downward movement of the electrode is obstructed.

4. In a system for automatically controlling the movement of electrodes in an electric furnace, the combination of an elec trode, a chain for movably suspending it, means responsive to electrical conditions in the furnace for controlling the movement of the electrode and means responsive to the tension in the chain for causing an alternate raising and lowering of the electrode when the downward movement of the electrode is obstructed.

5. In a system for automatically controlling the movement of electrodes in an electric furnace, the combination of an electrode. a chain for movably suspending it,

said chain having a portion disposed in a substantially horizontal plane, means re- I sponsive to electric conditions in the furnace or controlling the movement of the electrode, and means responsive to the tension 0 in the chain for causing an alternate raising. and lowering of the electrode when the downward movement of the electrode is obstructed, said last mentioned means including an element supported below the said horizontal portion for movement in a vertical plane, switch mechanism and means for translating movement of said element to the switch mechanism,

6. In a system for automatically controlling the movement of electrodes in an electric furnace, the combination of an electrode, a chain for movably suspending it, said chain having a portion disposed in a substantially horizontal plane, means responsive'to electric conditions in the furnace for controlling the movement of the electrode, and means responsive to the tension in the chain for causing an alternate raisin and lowering of the electrode when the ownward movement of the electrode is obstructed, said last mentioned means including a lever pivotally supported intermediate its ends and having a part disposed in the plane of movement of and below said horizontal chain portion, means on the lever tending to force the said part to an upper position, a switch and means operative to close the switch when said part is in its upper position and to open the switch when it is in a lower position.

7. In a system for automatically controlling the movement of electrodes in an electric furnace, the combination of an electrode a chain for movably suspending it, said chain having a portion disposed in a substantially horizontal plane, a lever pivotally supported intermediate its ends, one end of said lever intersecting the vertical motion of the'chain, a weight on the other end of the lever tending to force the said lirst end to an upper position, a switch mechanism and means on the lever for opening the switch when said first end is moved away from its upper position.

8. In a system for automatically controlling the movement of electrodes in an electric furnace, the combination of an electrode, a chain for suspending the electrode, said chain having a portion disposed in a substantially horizontal plane, means connected with the chain for raising and lowering the electrode and means for controlling said means, said controlling means including an element yieldingly disposed in the plane of and below the horizontal portion of the chain and adapted to be depressed by the sagging of the chain and means for translating the movement of the element.

In testimony whereof, I affix my signature.

THOMAS E. NIBLOCK.

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